The present invention relates to a flexible tube filled with a substance which expands on contact with water, the tube being wholly or partly of a material which loses consistency on contact with water, enabling said substance to expand.
As is known to the expert of the art, if for any reason water enters energy transportation or telecommunications cables (whether electricity conductor cables or fibre optic cables), the cable undergoes damage. The damage is greater the longer the cable portion into which the water has penetrated. This drawback is particularly damaging for fibre optic cables. Any water which accidentally enters the outer cable sheath must therefore be prevented from flowing along it and aggravating the damage. To achieve this result, powdered or granular acrylate is disposed between the conductive wires or optical fibres during cable manufacture (so that it lies on the inside of the sheath). This material has the property of swelling considerably on contact with water to create a xe2x80x9cplugxe2x80x9d which blocks water passage. The acrylate hence performs that function known to cable manufacturers as water blocking, the acrylate powder being known as WB powder.
However acrylate is known in this sector to be an extremely dangerous material, which must be handled with maximum care by cable manufacturing operators. In this respect, if inhaled, the bronchial tubes swell and become blocked.
The machines currently used by cable manufacturers to construct cables are machines which have been designed taking account of all the complex operations involved in cable manufacture, however the WB powder problem has been ignored, this being a problem which has arisen only recently. The solution could be to enclose such a machine in an air-tight container with a suction and powder removal system, however this would involve problems including high cost.
Cable manufacturers are therefore particularly interested in anything which can reduce the risks or simplify safety procedures accompanying the manufacture of such cables.
An object of the present invention is therefore to find a simple and economical solution to the aforestated problem.
The said object is attained by a flexible tube filled with a substance which expands on contact with water, the tube being wholly or partly formed of a material which loses consistency on contact with water, enabling said substance to expand.